This R21/R33 application is a test of concept study and potentially able to facilitate the development of novel non-traditional therapeutics that provides alternative treatment for infected patients. Emerging antibiotic-resistant strains of bacteria pose a significant threat to general health and welfare. Phagocytosis, along with other innate immune responses, exerts crucial impacts on the outcomes of the patients suffered from bacterial infections. In this proposal, we will use macrophages as a cellular model to develop a novel approach in order to enhance the myeloid cell-mediated phagocytosis and clearance of antibiotic-resistant bacteria. Based on our published and preliminary data, we found that miR-15a/16 attenuates phagocytosis and bacterial clearance by targeting on the TLR4-associated pathways in vitro. Deletion of miR-15a/16 (miR- 15a/16-/-) in myeloid cells significantly decreases the bacterial infection-associated mortality in septic mice. Consistently, miR-15a/16 deficiency (miR-15a/16-/-) results in augmented phagocytosis and generation of bactericidal reactive oxygen species (ROS) in macrophages. Our preliminary data further showed that bacteria and their derivatives robustly enhanced the release of exosomes. Interestingly, many secreted miR-15a/16 were released via exosome-shuttled manner (preliminary data). We therefore propose to develop miR-15a/16 inhibitor-enriched exosomes and hypothesize that these miR-15a/16 inhibitor-enriched exosomes can significantly enhance phagocyte-mediated bacterial clearance and improve the outcomes after bacterial infection. This high-risk/high-reward approach is fundamentally different from traditional microbicidal strategies that target the bacteria themselves, and is expected to be highly complementary with direct antibiotic approaches. R21 phase aims are to confirm the effect of miR-15a/16 deficiency on the clearance of antibiotic-resistant bacteria and to generate the miR-15a/16 inhibitor-enriched exosomes R33 phase aims are: to characterize the uptake of miR-15a/16 inhibitor-enriched exosomes by phagocytes in vivo and to assess the toxicity and inflammatory effects of miR-15a/16 inhibitor-enriched exosomes.